What is Octane and why some shouldn't use 93 or more

[2point4DSM]

Manufacturers have figured out what octane works best for our car, stock. Still some people think using high octane in a car that requires only 87 will improve performance when it doesn't.

Agree/Disagree AND discuss.

Btw, the Pilot and Saturn will only ever drink 87 octane. :)

The GSX seems to like 94 but hates anything less than 93.

[igo4bmx]

agreed

[silver05bullet]

The cars for which in the manual it says regular gas is sufficient are optimized to use the lower octane rated gasoline, and at the same time will not see a noticeable improvement in performance from using 93 or higher.

[S4toSTI]

I could be talking out my ass but won't a car make more power on a lower octane if it can use it with out knocking???

[2point4DSM]

I could be talking out my ass but won't a car make more power on a lower octane if it can use it with out knocking???

Absolutely right... as far as I know, lol

[teh DIRT]

alot of ecus cant read aboce 89...mine is one of them. BUT if you are tuning yourself with an aftermarket EM than the higher the better.

[S4toSTI]

Basically tho a car from the factory tuned to 87 doesn't need the higher octane cause it is not knocking so in essense it is producing the most ammmount of power on the 87.

[1988 Olds]

True, like Pete said only use higher octance if your reprogramming the ECU or just like spending money.

[Intercooled T]

knock sucks.

[snakeeyes]

alot of ecus cant read aboce 89...mine is one of them. BUT if you are tuning yourself with an aftermarket EM than the higher the better.


ecus dont read octane....... they get feedback from knock sensors

if your engine pings or knocks then using higher octane will reduce the likelihood of detonation

[xEJ20x]

knock sucks.

Best response EVAR!


But sersiously.
To avoid damage to your engine, run the reccommended octance rating for your car.
Is saving a few cents worth blowing an engine and spending a few thousand for a new one?

[95nracer]

Teh van only sees 87 thats all thats needed for it. I remember being at the gas station and some guy in a older cavalier was filing with 93 and he said he only fills with the best. The only thing I did was :roll:

The car usually only gets 93. Sometimes 94 and sometimes 93 with higher octane mix.

[WhiteXFire]

We were just discussing this on another forum when someone asked if he should put 110 race pump into the crossfire. The suggested octane for the car is what it is optimized for, such that it will burn without detonation and cause knock. The higher the octane, the more resistant it is to knock. In other words, it's how much you can compress it without it igniting as a result of the compression instead of the spark from the plugs. So, on a car without custom tuning, the best gas to use is the lowest possible octane that will not result in knock. Knock will rob you of hp, but higher octane will not give you hp unless your ECU is tuned to adjust timing (advance) to allow for more compression (later ignition). As was already stated, most ECU's will only retard ignition timing as a result of knock. Also, lower octane gas is faster burning than higher octane gas. So, running higher octane gas when unnecessary results in a longer burn time, and can actually hurt performance.

People keep asking me why I have to put premium in the crossfire. My engine has a compression of 10:1, whereas the new STi only has 8.2:1. Higher compression equals higher octane.

[S4toSTI]

Well that is engine compression not overall compression... ie ad the turbo into the equation.

[2point4DSM]

People keep asking me why I have to put premium in the crossfire. My engine has a compression of 10:1.

A lot of motors with 10:1 use 87 octane. In your instance it has to do with timing advance due to the ecu maps being more aggresive than on a stock Honda, for example.

I've got a logger and can see knock on the DSM when I use less than 93. I can hear knock in the Honda when I get a really bad batch of gas in Jersey, lol. I can hear it in a lot of cars as well. Just like in my parent's camry with 230k on the motor. They drive it like old farts and the motor is probably really tight otherwise except the buildup of carbon that is causing the higher compression and knock. So even if it were tuned for 87 it runs best on 93, lol.

[2point4DSM]

The cars for which in the manual it says regular gas is sufficient are optimized to use the lower octane rated gasoline, and at the same time will not see a noticeable improvement in performance from using 93 or higher.

Unless the car blew a headgasket at one point, the machine shop cut a lot off the head therefore increasing compression and or the shop that put the motor back together didn't bother to set base timing correctly and therefore has it wildly advanced, lol.

[WhiteXFire]

A lot of motors with 10:1 use 87 octane. In your instance it has to do with timing advance due to the ecu maps being more aggresive than on a stock Honda, for example.

I've got a logger and can see knock on the DSM when I use less than 93. I can hear knock in the Honda when I get a really bad batch of gas in Jersey, lol. I can hear it in a lot of cars as well. Just like in my parent's camry with 230k on the motor. They drive it like old farts and the motor is probably really tight otherwise except the buildup of carbon that is causing the higher compression and knock. So even if it were tuned for 87 it runs best on 93, lol.
Ok, that makes sense to me too. I don't know off-hand the compression ratios of most cars, so I looked up the STi as a frame of reference. I also have a custom chip to advance timing even further, specific to 93 and 94 octane, so it would be REALLY bad to run regular.

[S4toSTI]

Ok, that makes sense to me too. I don't know off-hand the compression ratios of most cars, so I looked up the STi as a frame of reference. I also have a custom chip to advance timing even further, specific to 93 and 94 octane, so it would be REALLY bad to run regular.
Then i would cross out "cross" and write "on"

[WhiteXFire]

Then i would cross out "cross" and write "on"
Har har har. :)

Here's a good overview:
http://www.leeric.lsu.edu/bgbb/7/ecep/trans/b/b.htm

[2point4DSM]

Btw, the reason people should run their car at WOT every once in a while is cause carbon will build-up in the motor and exhaust if you don't. If the car is hesitating or sounds like it is making some pinging noise then let off and get some higher octane gas, lol.

Of course, if the car/motor isn't built for WOT runs then forget it, lol.

[S4toSTI]

Btw, the reason people should run their car at WOT every once in a while is cause carbon will build-up in the motor and exhaust if you don't. If the car is hesitating or sounds like it is making some pinging noise then let off and get some higher octane gas, lol.

Of course, if the car/motor isn't built for WOT runs then forget it, lol.
I don't think mercedes' desguised as domestics are built for it.

[snakeeyes]

People keep asking me why I have to put premium in the crossfire. My engine has a compression of 10:1, whereas the new STi only has 8.2:1. Higher compression equals higher octane.

that's static compression
take a guess at what happens to the stis compression after the turbo spools

[WhiteXFire]

Yes, I know...more compressed air is packed into the cylinder chamber...bad example. Upon further review, I should have just said it was 10:1 and tuned from the factory to run on premium 91. And Barry, what does that mean, haha.

[95nracer]

people should run their car at WOT every once in a while .


I redline my car daily. :cool:

[ScoobyNubieToo!]

All I can say about that is that I use nothing but 93 in my 1997 Ford Escort. I beat the hell out of it and I got 280,000 miles on the original engine and fuel injectors. I think that says something.

[Chair-Force]

Manufacturers have figured out what octane works best for our car, stock. Still some people think using high octane in a car that requires only 87 will improve performance when it doesn't.

Agree/Disagree AND discuss.

Btw, the Pilot and Saturn will only ever drink 87 octane. :)

The GSX seems to like 94 but hates anything less than 93.
Not to mention using higher octane then recommended by the car maker can lead to a dirty, despoit-filled engine. Also, its just a waste of money.

[vwcorradokid]

It's very possible to tune a car properly on low octane gas without knock. It was recently done in Arizona by Precision Dyno Tuning. Nick unknowingly tuned an Evo that was running 87 octane. He found out afterwards and was amazed that it can be done. The owner of the Evo wanted to prove a point...and just that he did. Here's the url for that thread:

http://forums.evolutionm.net/showthread.php?t=169732

[ScoobyNubieToo!]

Not to mention using higher octane then recommended by the car maker can lead to a dirty, despoit-filled engine. Also, its just a waste of money.
Read my post above yours and explain how, please :cool:

[2point4DSM]

It's very possible to tune a car properly on low octane gas without knock.

No doubt. Just like it's possible to tune a 10:1 compression motor on 87 octane while other cars like the Crossfire are stuck with 93 or more.

I understand the chemistry/physics of water-injection. I've had years of both chemistry and physics through HS and college.

My opinion is I would rather run 93/94 octane all the time rather than have to worry about whether or not I have enough water to run, for example, with a vette that just came out of no-where. To me water-injection is just one more thing you have to watch and worry about, and for me that would be in addition to the numerous gauges and tuning devices in my car, already. Personally, I try to focus first on the road, then possible trouble around me, and then the car.

If you really want to go all out, frankly, water-injection seems like a waste of time cause nitrous actually has similar properties but then also adds power.

I'm sure there will be several people for and against what I said. Ultimately it comes down to economics and tuning/performance goals. Some want to go as fast as possible with as little money as possible. Some want to go fast and have all the bases covered. And there is the plethora of people in btw. I use to be in the camp that tried to max out every single component before I went with bigger parts. The inherent draw back to that way of thinking is parts tend to blow up faster that way, lol.
:cool:

[capaGC8]

If you're talking strictly about 110 octane then you could definitely see some damage from using gas with a such ridiculously high rating on a stock car.

Now, i don't know if you can say the same between 87 and 93. the only drawback is the extra money, but you're paying extra for piece of mind. the only thing you can do wrong with pump gas is use too low of a rating - never too high.

With ECU controlled fuel injection, there's no saying a car is set to a particular octane rating. Especially when it's only a difference of 6 octane.

With carbs and distributor caps 6 might make a difference.

[Chair-Force]

Read my post above yours and explain how, please :cool:
We had a ASE fact book in my old shop and according to ASE, higher then recommended octane is unhealthly for an engine. I'd believe ASE over some average Joe's opinion.
Maybe your car is the spawn of the Devil or OPEC.

[07BlackSS]

This can truely be me talking out of my ass but for some wierd reason I get better Miles per gallon on my honda with 93 compared to 87? Has anyone else seen this?

[ScoobyNubieToo!]

We had a ASE fact book in my old shop and according to ASE, higher then recommended octane is unhealthly for an engine. I'd believe ASE over some average Joe's opinion.
Maybe your car is the spawn of the Devil or OPEC.My statement is not opinion, it's fact. I guess my car is a freak of nature. :mrgreen:

[2point4DSM]

Maybe it has a lot to do with how you drive the car as well. A person who has a car tuned for 87 and drives it really slow would definitely see a lot of carbon deposit/build up from using higher octane gas.

On the other hand a person who drives the snot out of their car wouldn't have to worry about carbon build-up as much due to ocassional to consistently running the motor at WOT. :)

[vwcorradokid]

Maybe it has a lot to do with how you drive the car as well. A person who has a car tuned for 87 and drives it really slow would definitely see a lot of carbon deposit/build up from using higher octane gas.

On the other hand a person who drives the snot out of their car wouldn't have to worry about carbon build-up as much due to ocassional to consistently running the motor at WOT. :)

Just drive it like you stole it and everything will be nice and sparkly on the inside. I can believe this just from my personal experience with driving like a retard. I have 2 positions for my gas pedal...all the way up or thru the firewall. I've never seen anyone get 20mpg consistently in the city from an SUV like I have. I swear that short ram and cat-back really helped with my gas mileage.

[subwrxkid]

The cars for which in the manual it says regular gas is sufficient are optimized to use the lower octane rated gasoline, and at the same time will not see a noticeable improvement in performance from using 93 or higher.
omg cuz thats not plagerized...reguardless I totally agree!

[2Mopars1Ford]

It takes alot more to get full combustion out of higher octane.
So if your car is not tuned for it, doesn't have the right compression spark etc.... you won't be able to get a full clean burn which can lead to wasted gas, bad for cats and O2's and possible lower performance.

[1988 Olds]

Who has cats and O2s anyway.

[Intercooled T]

just go catless and get a denso o2...lead resistent and won't die from using racegas :)

[Zeropistonz]

Its all about the RON and MON

The formula (RON+MON)/2 is referred to as the anti-knock index.
RON = Research Octane Number (normal driving conditions)
MON = Motor Octane Number (severe driving conditions under high RPM)

higher octane fuels require more fuel to be burnt in order to produce the same amount of energy (additives to prevent knock), however if there is any sort of knock this will not hold true.

So the idea is to use the lowest octane fuel without the risk of knock.

[slavetothemuzic]

Here's more good info from How Stuff Works (http://auto.howstuffworks.com/question90.htm)